This invention relates to a compatible blend of two or more normally incompatible polymers. More particularly, this invention relates to blends of a first reactive polymer or polymer blend containing pendant cyclic iminoether groups and another reactive polymer or polymer blend containing groups which react with cyclic iminoether groups to form linkages between the reactive polymers or polymer blends. The subject invention is characterized by having at least one of the reactive polymers extended with a miscible but nonreactive polymer or polymers to form a reactive blend thereof.
It is often desirable to prepare blends of polymers which maximizes the desirable properties but minimizes the deficiencies of the component polymers. For example, monovinylidene aromatic polymers, such as polystyrene, have desirable properties such as being easily thermoformed and have good mechanical characteristics. However, such monovinylidene aromatic polymers have certain undesirable properties such as poor environmental stress crack resistance (ESCR). On the other hand, polyolefins such as polyethylene or polypropylene have relatively good ESCR and low temperature properties but are not as readily thermoformed as desired. It would be highly desirable to provide a blend of a monovinylidene aromatic polymer and other polyolefins which exhibits the desirable properties but not the deficiencies, of the component polymers. Similarly, it is often desirable to blend other polymers in like manner.
Unfortunately, however, such blends often do not exhibit these expected properties. Many such blends exhibit properties which are, in fact, far worse than those of the component polymers due to an incompatibility of the polymers. For example, monovinylidene aromatic polymers such as polystyrene and rubber modified polystyrene are notably incompatible with many polymers which would otherwise be advantageously blended therewith. Thus, most blends containing polystyrene and like polymers exhibit poorer than expected properties.
Various methods have been proposed to prepare blends of normally incompatible polymers. Generally, these methods have focused on the use of grafting techniques or the use of a third component, a compatiblizing agent, in the blend. For example, in U.S. Pat. Nos. 4,386,187 and 4,386,188 it is taught to prepare blends of polyolefins and a polystyrene using a styrene/butadiene/styrene block copolymer. Compatibilizing agents which are ethylene/vinylacetate copolymers, ethylene/acrylic acid ester copolymers and ethylene/methacrylic acid ester copolymers have also been taught for use in preparing blends of polystyrene and polyolefins (see Japanese Patent Announcement Kokai No. 48-43031/1973). Other such compatibilizing agents are taught in, for example, U.S. Pat. Nos. 4,188,432; 4,020,025; British Pat. No. 1,363,463 and German Pat. No. 241,375.
Unfortunately, these approaches to preparing compatible polymer blends often do not yield entirely satisfactory results. In many instances, the type and proportion of the component polymers which can be blended using these techniques is quite narrowly restricted. In addition, the inclusion of an additional component in the blend often has an adverse effect on the properties of the blend. However, the blend achieved is still not as compatible as desired and accordingly the properties of the blend are sometimes not as good as expected.
Accordingly, it would be desirable to provide a blend of normally incompatible polymers in which improved compatibilization of the polymers and improved properties of the blend are achieved. It is further desirable to be able to maximize the type and proportion of the desirable component polymers in any particular blend.
It has been discovered that in addition to reactive polymers which compatibilize normally incompatible polymers that unexpectedly these reactive polymers can be extended with miscible nonreactive polymers without a loss in blend compatibility.